Centrifugal compressor diffuser vanes



April 3, 1945. K. A. BROWNE CENTRIFUGAL COMPRESSOR DIFFUSER VANES File'd Jan. 11, 1944 IN V EN TOR. KENNETH A. BROWNE.

RNEY

Patented Apr. 3, 1945 UNITED STATES PATENT ori ice CENTRIFUGAL COMPRESSOR. DIFFUSER.

VANES Kenneth A. Browne, Ridgewood, N. J., assignor to Wright Aeronautical Corporation, a corporation of New York Application January 11, 1944, Serial No. 517,867

6 Claims.

sion is disposed approximately in the direction of the exit flow-path of the fluid discharged from the impeller.

It has been found that there is considerable variation in the radial component of the fluid discharge velocity axially across the discharge end of the impeller, the radial component of this velocity being greatest adjacent to the back Wall of-the impeller. In order to efficiently handle this uneven flow, it is an object of this invention to so-dispose the diffuser vanes that the effective width of the fluid path between the vanes is greatest at the back wall of the impeller in order to accommodate the larger flow adjacent to this wall. Specifically, instead of disposing the diffuser vanes axially across the diffuser chamber, each of these vanes is twisted in such a manner that its rear longitudinal edge makes a larger angle with a tangent to the periphery of the impeller, adjacent the inner edge of the diffuser vanes, than its front longitudinal edge.

Other objects of the invention will become apparent upon reading the annexed detailed description in connection with the drawing in which:

Fig. 1 is a front view of a centrifugal impeller extend transversely across the chamber, e. g., the diffuser vanes 26 may be formed integral with either the front or the rear wall of the diffuser chamber 24. If desired, these vanes may be pivotally mounted, about an axis parallel to the axis of the impeller. The inner ends of these vanes are disposed about the periphery of the impeller and approximately extend therefrom in the directionof the fluid flow leavin the impeller. From the diffuser chamber, the fluid is received in an annular manifold 28, from whence it is distributed to the various cylinders of the engine. Except for the specific shape A the difiuser vanes, as illustrated in the drawing, the structure so far described is conventional.

The conventional supercharger for an aircraft engine has a large entrance opening in order to give the supercharger a large specific capacity and, as a result, the relative tangential velocity tively ineffective in converting the relative tangential velocity of the entering fluid into pressure. Therefore, there is a tendency for the impeller to induce a higher entrance velocity towardthe impeller hub than at the outer periphery of the entrance edges of the vanes, as

indicated by the velocity flow vectors A, B, and C in Fig. 2. 'In addition, the velocity of a fluid after leaving a 90 bend is not uniform and tends to be highest adjacent to the outside wall of the bend. Both of these effects combine to increase the radial component of the fluid discharge velocity at with difiuser vanes embodying the invention, and

Fig. 2 is an axial section takenalong line 2-2 of Fig l.

Referring to the drawing, a conventional aircraft engine supercharger is provided with a centrifugal impeller 10 having vanes l2 extend- .ing radially from the impeller hub M. The vanes are formed with the usual bent entrance portions 16 designed to minimize the impact of the entering fluid with the impeller vanes. The impeller hub I l is provided with integral splines 18 to the back of the vanes, as compared to the radial component in'front of the vanes, e. g., as indicated on the'drawing by the radial vector coma ponents A, B, and C. The tangential component of the fluid discharge velocity is constant in magnitude across the impeller and is equal to the-impeller peripheral speed u, so that the absolute velocity of the radial components A, B, and C may be indicated by the vectors A", B", and C", as in Fig. 1.

The capacity of the compressor is limited by the effective area of the fluid flow-path between the diffuser vanes; however, the efficiency of compression is 'a maximum at a flow corresponding to a constant ratio, less than one, of the velocity of the fluid at the diffuser entrance to the theoretical fluid discharge velocity, illustrated on the drawby vectors A", B" and C". To obtain this highest possible efliciency, this ratio should be constant across the diffuser passage. Therefore, the effective width of the fluid flow-path between adjacent diiIuser vanes should be larger adjacent to the back wall of the diffuser chamber than the width of this path adjacent to the front wall. Applicant accomplishes this result by twisting each of the difiuser vanes from its usual axial disposition, such that the rear edge of each vane makes a larger angle to the tangent to the impeller periphery adjacent the inner end of the vane than the front edge of the vane. As illustrated, the vanes are symmetrically twisted about a mid-section which remains axial. However, this constructionis not essential; e. g., the vanes may be twisted so that either end of the vanes remains axial. It is only essential that each of the vanes be twisted in such a manner that the axial variation in the effective width of the fluid flow-path between the vanes corresponds to the variation of the fluid discharge velocity axially across the difiuser chamber. Also, each one of the diffuser vanes may readily be mounted for pivotal adjustment about an axis at its untwisted or axial portion;

e. 8., the vanes illustrated may be pivotally mounted for adjustment about their mid-sections.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modifications and changes.

I claim as my invention:

1. In a fluid blower having a diffuser chamber, a plurality of difiuser vanes disposed across said chamber, said vanes being disposed so that each pair of adjacent vanes provides a, fluid flow path therebetween through said chamber, with width of said flow paths being variable such that said width is a maximum at the point of maximum velocity of the fluid entering said flow path.

2. In a centrifugal fluid compressor having an annular impeller and an annular difluser chamber disposed thereabout, a plurality of'ci'rcumferentially spaced diiluser vanes disposed across said chamber, said vanes being arranged so that each pair of adjacent vanes provides a fluid flow path therebetween through said chamber, the width of said flow paths being variable axially across said vanes such that said width is a maximum at the point of maximum velocity of the fluid entering said flow path.

3. In a centrifugal compressor having anannular impeller and an annular diffuser chamber receiving the output of said impeller, a plurality of diffuser vanes disposed across said chamber, said vanes being so arranged that the effective width of the fluid flow-path between adjacent vanes varies axially across the chamber substantially in accordance with the axial variation in the magnitude of the velocity of the fluid flowing through said chamber.

4. In a centrifugal compressor having an annular impeller and a diffuser chamber disposed about the discharge end of said impeller, a plurality of circumferentially spaced diffuser vanes disposed across said chamber, each one of said vanes being so arranged that a tangent to the impeller periphery adjacent to the back end of said vane makes a larger angle with the rear longitudinal edge of said vane than with its front longitudinal edge.

5. In a centrifugal compressor having an annular impeller and a diffuser chamber disposed about the discharge end of said impeller, a plurality of circumferentially spaced difiuser vanes disposed across said chamber, said vanes being so arranged that the effective width of the fluid path between these vanes adjacent the back of said chamber is larger than adjacent the front of said chamber.

6. In a centrifugal compressor having an annular impeller and an annular diffuser chamber disposed about the discharge end of said impeller, a plurality of circumferentially spaced diffuser vanes disposed across said chamber, said vanes being twisted such that the effective width of the fluid flow-path between these vanes is larger adjacent the back of said vanes than adjacent the front of said vanes.

KENNETH A. BROWNE. 

